A hydrocyclone plant of the general kind described is known from U.S. Pat. No. 4,190,523, in which each hydrocyclone group forms a disc having a number of radially oriented hydrocyclones, said disc-shaped hydrocyclone groups being stacked. This known plant is not practical to use for applications which require relatively long hydrocyclones, since the discs would be too large and heavy. For instance, when cleaning fiber pulp suspensions by means of this plant, the required long hydrocyclones would result in discs having a diameter exceeding two metres. Such large discs would be difficult to disassemble from the stack of discs for servicing and repairing individual hydrocyclones. The object of the present invention is to provide a hydrocyclone plant of this kind, which is compact, is suited for relatively long hydrocyclones, and enables easy servicing of the individual hydrocyclones.